Thin indium tin oxide (ITO) films have been deposited onto polycarbonate (PC) substrate without substrate heating by direct metal ion beam deposition (DMIBD) technique and the influence of secondary negative metal ion beam energy on the opto-electrical and surface morphological property of the films have been investigated. For ITO films (100 nm thick) deposited at ion beam energy of 50 eV, the lowest resistivity and the highest optical transmittance was obtained but when using higher ion beam energy (above 75 eV) both conductivity and optical transmittance were decreased. Surface roughness of as deposited ITO thin film at 50 eV is less than that of the bare PC substrate. However, too intense ion beam bombardment on growing film deteriorated the opto-electrical property of ITO films. XPS measurements showed that ITO films grown at 50 eV were fully oxidized and Cs 3d(5) peak is also observed. In this study, by using DMIBD technique we were able to obtain ITO films on PC substrate with 5 x 10(-4) Omega cm and above 90% optical transmittance at 550 nm. (C) 2003 Published by Elsevier Science B.V.